Any of the rod-shaped, usually gram-positive bacteria (see gram stain ) that make up the genus Clostridium.
They are found in soil, water, and the intestinal tracts of humans and other animals. Some species grow only in the complete absence of oxygen. Dormant cells are highly resistant to heat, drying, toxic chemicals, and detergents. The toxins produced by C. botulinum, which causes botulism , are the strongest poisons known. The toxin of C. tetani causes tetanus ; other species can cause gangrene .